The use of a totem animal is not part of traditional Wiccan practice. However, as Wicca and other modern Pagan practices evolve and blend together, many people who follow non-mainstream spiritual paths find themselves working with a mix of many different belief systems. Because of this, someone following a Native American or Indo-European shamanic path might find themselves working with totem animals. While totem animals or power animals have nothing to do with the Wiccan religion, some people do incorporate them into non-Wiccan shamanic practices as well as Neowiccan eclecticism.
It should be pointed out that sometimes, the use of totem animals and other Native American practices is sometimes seen as cultural appropriation when it's done by non-Native American individuals. Some European shamanic systems do connect with animal spirits, but the use of the specific word "totem" implies a Native American connection. It has a very specific, anthropological meaning, and chances are that if you have made a spiritual connection with an animal entity, it does not qualify as a true "totem." Be cautious what you call your beliefs, because you may find yourself taking ownership of a heritage that's not actually yours to claim. If you're not Native American, but are practicing some other form of shamanism, you may want to consider using the term "power animal" or even "spirit animal" instead.
A power animal is a spiritual guardian that some people connect with. However, much like other spiritual entities, there's no rule or guideline that says you must have one. If you happen to connect with an animal entity while meditating or performing astral travel, then that may be your power animal… or it may just be curious about what you're up to. Our Guide to Healing, Phylameana lila Desy, has a great piece on different types of animal totems and what they mean: Animal Totems.
Unfortunately, as often is seen in the Pagan community, many times the connection to a power animal is simply the result of wishful thinking. When someone tells you they have a spirit animal, they'll almost always tell you it's the bear, the eagle, or the wolf. Why? Because these are animals that exemplify the characteristics we'd really like to see in ourselves -- we want to be strong and formidable like Bear, independent and mysterious like Wolf, or all-seeing like Eagle. No one will every tell you their "totem animal" is the wombat, the hedgehog, or the three-toed sloth.
There are a number of books available that discuss the spiritual nature of animals. Nearly all will tell you to "choose" your spirit animal based upon which animals you want to see first at the zoo or which ones you just find really interesting. Generally, in true shamanic practice, one meets their power animal through meditation or a vision quest. Often, it's an animal you never expected to encounter. If you are fortunate enough to have this take place, do some research on the animal you've connected with, and find out why that particular creature has attached itself to you. Animals have different symbolism in different cultures and societies. Take the time to do some research, and you may end up learning something new about yourself.